Mesodermal cells are derived from a number of tissues and act as the supportive structure for other cell types. Bone marrow for instance is made of both haematopoietic and mesenchymal derived cells. Two principle mesenchymal cell types have been previously described and characterized, namely (i) mesenchymal stem cells (MSCs) and their precursors and (ii) mesenchymal precursor cells (MPCs) found in the bone marrow. Mesenchymal stem cells (MSCs) are multipotent, adult stem cells. MSCs differentiate to form the different specialised cells found in the skeletal tissues. For example, they can differentiate into cartilage cells (chondrocytes), bone cells (osteoblasts) and fat cells (adipocytes).
MSCs are already used in a variety of therapies, such as the treatment of Age-related Macular Degeneration (AMD) and myocardial infarct. Once administered to the subject, the MSCs typically migrate (or home) to the damaged tissue and exert their therapeutic effects through paracrine signaling and by promoting survival, repair and regeneration of the neighbouring cells in the damaged tissue.
There is some evidence to suggest that MSCs may possess certain immunosuppressive and immune-enhancing properties. MSCs could therefore be used to manipulate immune responses and thereby treat diseases. However, current therapies typically involve the infusion of a mixture of MSC subtypes, most of which do not possess the required immuno-modulatory properties. This necessitates the use of a high cell-dose which can lead to off-target side effects and volume-related side effects. Furthermore, MSCs are typically obtained from bone marrow and so it is difficult to obtain the large numbers of cells needed for this approach.